Manufacture of methacrylonitrile



2'5. repress the I Iaceto'ne' cyanohydrine with Patented Aug. 6, 1940 v UNITED STATES 2,210,320 MANUFACTURE or ME'rnAcaYLom'ramn Carl T. Kautter,

Heinz Grate, many, assignors Philadelphia, Pa.

No Drawing. Application rial No. 248,212. In

4 Claims.

This invention relates to a process for the production of methylacrylonitrile. It relates particularly to a process of dehydrating acetone cyanohydrine by means of halides or oxyhalides g of phosphorus or sulfur according to which there is a simultaneous production of methacrylonitrile and 11-11310 isobutyronitrile.

It is known that phosphorus pentoxide will dehydrate acetone cyanhydrine to form methals) crylonitrile but this method has several disadvantages, particularly in large scale operations. In the first place phosphorus pentoxide is a very hygroscopic material and diflicult in the factory. In the second place the yields of it methacrylonitrile are very low so that the process isnot an economical one.

.It is anobject of this invention to provide a method for preparing methacrylonitrile in good yield. along with some a-halo isobutyronitrile 20 whichcan subsequently be converted to the methacrylonitrile v v it. desired. It is a further obiect to carry out therea'ction between acetone :Cyanohydrine andthehalide or oxyhalide of phos- "phorous or (sulfur :undersu'h conditions'as to forma tion'of the halogenated nitrile. These objects 'are accomplished by treating the phosphorus pentachloride. phosphorus oxychlorl'de or thionyl chloride at an elevated ternperaztture.-

ierred compound. is thionyl :jf hloride because hen this reacts with water all the products are gaseous and can-be readily removed from the reactionmixture; The phosphorus compounds also give goodresultsjbut are somewhat more 35 diflicult to handle-on'account oi the necessity of separating the phosphoric acid formed from the desired products.

In carrying out this process there is always some m-chloroisobutyronitrile formed but it has of 75 to 100 and distilling out the product as it is formed, the amount of the a-chloroisobutyronitrile in the product can be considerably re-' duced. It has also been found that the amount of the chlorinated nitrile can be reduced by addsulfur halide to the aces ing the phosphorus or tone cyanohydrine at about the same rate as that at which it is consumed at the above mentioned temperature. The methacrylonitrile disso tills about as fast as it is formed and can then be purified or subjected to further treatment.

The formation of the u-chloroisobutyronitrile can be still further repressed by adding a base to the acetone cyanehydrine to absorb the hydrogen l6 chloride which is evolved.

Darmstadt, Frankfort-on-the-Maln,

to Rs'ihm & Haas Company,

to handle been found that by operating at temperaturesand Albert Robert Ger- December 29, 1938, Se-

Germany December 30,

The invention may be lowing examples but it illustrated by the 101- is not limited to the relative amounts of reagents, time of heating or temperature, as it may otherwise be practiced within the scope of the appended claims.

Example 1.-173 grams of 98% pure acetone cyanohydrine is mixed with 250 grams of thionyl chloride and heated. The reaction begins at about 65 C. and the mass is heated for seven hours on a water bath under a reflux condenser. The product obtained after cooling is washed with water and soda solution and iractionally distilled. The yield is about 40% of methacrylonitrile and 40% of a-chloroisobutyronitrile.

Example 2.-85 grams of 97.5% pure acetone cyanohydrine is heated on a water bath to about 85 C. 119 grams of thionyl chloride is dropped in in the course of an hour. During this time the temperature rises to about 96 and a pale yellow liquid distills over. After all of the thionyl chloride has been added the temperature is raised to about 150 whereupon more liquid distills over. The distillate is soda solution and fractionated. The yield is about 50% of methacrylonitrile and 35% of a-chloroisobutyronitrile.

The u-chloroisobutyronitrile can be converted into valuable compounds according to known methods, for example, to a-chloroisobutyric acid esters or, by splitting out hydrogen chloride, to methacrylonitrile.

We claim:

1. The process of simultaneously producin methacrylonitrile and a-chloroisobutyronitrile which comprises treating acetone cyanohydrine with thionyl chloride.

2. The process of simultaneously producing methacrylonitrile and a-chloroisobutyronitrile which comprises treating acetone cyanohydrine with thionyl chloride at temperatures of about 75 to about 100 C.

3. The process of simultaneously producing 'methacrylonitrile and u-chloroisobutyronitrile which comprises treating acetone cyanohydrine with thionyl chloride at temperatures of about '75 -,to about 100 C. and distilling the methacrylonitrile as it is formed.

4. The process which comprises heating acetone cyanohydrine to about 85 0. adding thionyl chloride thereto at about the rate at whichit is consumed and distilling out methacrylonitrile as it is .iormed. 

